Source/core/rendering/RenderFlexibleBox.cpp

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This source file includes following definitions.
m_numberOfInFlowChildrenOnFirstLine
createAnonymous
renderName
computeIntrinsicLogicalWidths
synthesizedBaselineFromContentBox
baselinePosition
firstLineBoxBaseline
inlineBlockBaseline
resolveAlignment
removeChild
styleDidChange
layoutBlock
appendChildFrameRects
repaintChildrenDuringLayoutIfMoved
paintChildren
repositionLogicalHeightDependentFlexItems
clientLogicalBottomAfterRepositioning
hasOrthogonalFlow
isColumnFlow
isHorizontalFlow
isLeftToRightFlow
isMultiline
flexBasisForChild
setCrossAxisExtent
crossAxisExtentForChild
mainAxisExtentForChild
crossAxisExtent
mainAxisExtent
crossAxisContentExtent
mainAxisContentExtent
computeMainAxisExtentForChild
transformedWritingMode
flowAwareBorderStart
flowAwareBorderEnd
flowAwareBorderBefore
flowAwareBorderAfter
flowAwarePaddingStart
flowAwarePaddingEnd
flowAwarePaddingBefore
flowAwarePaddingAfter
flowAwareMarginStartForChild
flowAwareMarginEndForChild
flowAwareMarginBeforeForChild
flowAwareMarginAfterForChild
crossAxisMarginExtentForChild
crossAxisScrollbarExtent
flowAwareLocationForChild
setFlowAwareLocationForChild
mainAxisBorderAndPaddingExtentForChild
mainAxisScrollbarExtentForChild
preferredMainAxisExtentDependsOnLayout
childPreferredMainAxisContentExtentRequiresLayout
preferredMainAxisContentExtentForChild
layoutFlexItems
autoMarginOffsetInMainAxis
updateAutoMarginsInMainAxis
hasAutoMarginsInCrossAxis
availableAlignmentSpaceForChild
updateAutoMarginsInCrossAxis
marginBoxAscentForChild
computeChildMarginValue
prepareOrderIteratorAndMargins
adjustChildSizeForMinAndMax
computeNextFlexLine
freezeViolations
resolveFlexibleLengths
initialJustifyContentOffset
justifyContentSpaceBetweenChildren
setLogicalOverrideSize
prepareChildForPositionedLayout
alignmentForChild
numberOfInFlowPositionedChildren
resetAutoMarginsAndLogicalTopInCrossAxis
layoutAndPlaceChildren
layoutColumnReverse
initialAlignContentOffset
alignContentSpaceBetweenChildren
alignFlexLines
adjustAlignmentForChild
alignChildren
applyStretchAlignmentToChild
flipForRightToLeftColumn
flipForWrapReverse
/*
 * Copyright (C) 2011 Google Inc. All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are
 * met:
 *
 *     * Redistributions of source code must retain the above copyright
 * notice, this list of conditions and the following disclaimer.
 *     * Redistributions in binary form must reproduce the above
 * copyright notice, this list of conditions and the following disclaimer
 * in the documentation and/or other materials provided with the
 * distribution.
 *     * Neither the name of Google Inc. nor the names of its
 * contributors may be used to endorse or promote products derived from
 * this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
 * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
 * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */

#include "config.h"
#include "core/rendering/RenderFlexibleBox.h"

#include "core/rendering/LayoutRectRecorder.h"
#include "core/rendering/LayoutRepainter.h"
#include "core/rendering/RenderLayer.h"
#include "core/rendering/RenderView.h"
#include "platform/LengthFunctions.h"
#include "wtf/MathExtras.h"
#include <limits>

namespace WebCore {

struct RenderFlexibleBox::LineContext {
    LineContext(LayoutUnit crossAxisOffset, LayoutUnit crossAxisExtent, size_t numberOfChildren, LayoutUnit maxAscent)
        : crossAxisOffset(crossAxisOffset)
        , crossAxisExtent(crossAxisExtent)
        , numberOfChildren(numberOfChildren)
        , maxAscent(maxAscent)
    {
    }

    LayoutUnit crossAxisOffset;
    LayoutUnit crossAxisExtent;
    size_t numberOfChildren;
    LayoutUnit maxAscent;
};

struct RenderFlexibleBox::Violation {
    Violation(RenderBox* child, LayoutUnit childSize)
        : child(child)
        , childSize(childSize)
    {
    }

    RenderBox* child;
    LayoutUnit childSize;
};


RenderFlexibleBox::RenderFlexibleBox(Element* element)
    : RenderBlock(element)
    , m_orderIterator(this)
    , m_numberOfInFlowChildrenOnFirstLine(-1)
{
    setChildrenInline(false); // All of our children must be block-level.
}

RenderFlexibleBox::~RenderFlexibleBox()
{
}

RenderFlexibleBox* RenderFlexibleBox::createAnonymous(Document* document)
{
    RenderFlexibleBox* renderer = new RenderFlexibleBox(0);
    renderer->setDocumentForAnonymous(document);
    return renderer;
}

const char* RenderFlexibleBox::renderName() const
{
    return "RenderFlexibleBox";
}

void RenderFlexibleBox::computeIntrinsicLogicalWidths(LayoutUnit& minLogicalWidth, LayoutUnit& maxLogicalWidth) const
{
    // FIXME: We're ignoring flex-basis here and we shouldn't. We can't start honoring it though until
    // the flex shorthand stops setting it to 0.
    // See https://bugs.webkit.org/show_bug.cgi?id=116117 and http://crbug.com/240765.
    for (RenderBox* child = firstChildBox(); child; child = child->nextSiblingBox()) {
        if (child->isOutOfFlowPositioned())
            continue;

        LayoutUnit margin = marginIntrinsicLogicalWidthForChild(child);
        bool hasOrthogonalWritingMode = child->isHorizontalWritingMode() != isHorizontalWritingMode();
        LayoutUnit minPreferredLogicalWidth = hasOrthogonalWritingMode ? child->logicalHeight() : child->minPreferredLogicalWidth();
        LayoutUnit maxPreferredLogicalWidth = hasOrthogonalWritingMode ? child->logicalHeight() : child->maxPreferredLogicalWidth();
        minPreferredLogicalWidth += margin;
        maxPreferredLogicalWidth += margin;
        if (!isColumnFlow()) {
            maxLogicalWidth += maxPreferredLogicalWidth;
            if (isMultiline()) {
                // For multiline, the min preferred width is if you put a break between each item.
                minLogicalWidth = std::max(minLogicalWidth, minPreferredLogicalWidth);
            } else
                minLogicalWidth += minPreferredLogicalWidth;
        } else {
            minLogicalWidth = std::max(minPreferredLogicalWidth, minLogicalWidth);
            if (isMultiline()) {
                // For multiline, the max preferred width is if you never break between items.
                maxLogicalWidth += maxPreferredLogicalWidth;
            } else
                maxLogicalWidth = std::max(maxPreferredLogicalWidth, maxLogicalWidth);
        }
    }

    maxLogicalWidth = std::max(minLogicalWidth, maxLogicalWidth);

    LayoutUnit scrollbarWidth = instrinsicScrollbarLogicalWidth();
    maxLogicalWidth += scrollbarWidth;
    minLogicalWidth += scrollbarWidth;
}

static int synthesizedBaselineFromContentBox(const RenderBox* box, LineDirectionMode direction)
{
    return direction == HorizontalLine ? box->borderTop() + box->paddingTop() + box->contentHeight() : box->borderRight() + box->paddingRight() + box->contentWidth();
}

int RenderFlexibleBox::baselinePosition(FontBaseline, bool, LineDirectionMode direction, LinePositionMode mode) const
{
    ASSERT(mode == PositionOnContainingLine);
    int baseline = firstLineBoxBaseline();
    if (baseline == -1)
        baseline = synthesizedBaselineFromContentBox(this, direction);

    return beforeMarginInLineDirection(direction) + baseline;
}

int RenderFlexibleBox::firstLineBoxBaseline() const
{
    if (isWritingModeRoot() || m_numberOfInFlowChildrenOnFirstLine <= 0)
        return -1;
    RenderBox* baselineChild = 0;
    int childNumber = 0;
    for (RenderBox* child = m_orderIterator.first(); child; child = m_orderIterator.next()) {
        if (child->isOutOfFlowPositioned())
            continue;
        if (alignmentForChild(child) == ItemPositionBaseline && !hasAutoMarginsInCrossAxis(child)) {
            baselineChild = child;
            break;
        }
        if (!baselineChild)
            baselineChild = child;

        ++childNumber;
        if (childNumber == m_numberOfInFlowChildrenOnFirstLine)
            break;
    }

    if (!baselineChild)
        return -1;

    if (!isColumnFlow() && hasOrthogonalFlow(baselineChild))
        return crossAxisExtentForChild(baselineChild) + baselineChild->logicalTop();
    if (isColumnFlow() && !hasOrthogonalFlow(baselineChild))
        return mainAxisExtentForChild(baselineChild) + baselineChild->logicalTop();

    int baseline = baselineChild->firstLineBoxBaseline();
    if (baseline == -1) {
        // FIXME: We should pass |direction| into firstLineBoxBaseline and stop bailing out if we're a writing mode root.
        // This would also fix some cases where the flexbox is orthogonal to its container.
        LineDirectionMode direction = isHorizontalWritingMode() ? HorizontalLine : VerticalLine;
        return synthesizedBaselineFromContentBox(baselineChild, direction) + baselineChild->logicalTop();
    }

    return baseline + baselineChild->logicalTop();
}

int RenderFlexibleBox::inlineBlockBaseline(LineDirectionMode direction) const
{
    int baseline = firstLineBoxBaseline();
    if (baseline != -1)
        return baseline;

    int marginAscent = direction == HorizontalLine ? marginTop() : marginRight();
    return synthesizedBaselineFromContentBox(this, direction) + marginAscent;
}

static ItemPosition resolveAlignment(const RenderStyle* parentStyle, const RenderStyle* childStyle)
{
    ItemPosition align = childStyle->alignSelf();
    if (align == ItemPositionAuto)
        align = parentStyle->alignItems();
    return align;
}

void RenderFlexibleBox::removeChild(RenderObject* child)
{
    RenderBlock::removeChild(child);
    m_intrinsicSizeAlongMainAxis.remove(child);
}

void RenderFlexibleBox::styleDidChange(StyleDifference diff, const RenderStyle* oldStyle)
{
    RenderBlock::styleDidChange(diff, oldStyle);

    if (oldStyle && oldStyle->alignItems() == ItemPositionStretch && diff == StyleDifferenceLayout) {
        // Flex items that were previously stretching need to be relayed out so we can compute new available cross axis space.
        // This is only necessary for stretching since other alignment values don't change the size of the box.
        for (RenderBox* child = firstChildBox(); child; child = child->nextSiblingBox()) {
            ItemPosition previousAlignment = resolveAlignment(oldStyle, child->style());
            if (previousAlignment == ItemPositionStretch && previousAlignment != resolveAlignment(style(), child->style()))
                child->setChildNeedsLayout(MarkOnlyThis);
        }
    }
}

void RenderFlexibleBox::layoutBlock(bool relayoutChildren)
{
    ASSERT(needsLayout());

    if (!relayoutChildren && simplifiedLayout())
        return;

    LayoutRepainter repainter(*this, checkForRepaintDuringLayout());
    LayoutRectRecorder recorder(*this);

    if (updateLogicalWidthAndColumnWidth())
        relayoutChildren = true;

    LayoutUnit previousHeight = logicalHeight();
    setLogicalHeight(borderAndPaddingLogicalHeight() + scrollbarLogicalHeight());

    {
        LayoutStateMaintainer statePusher(*this, locationOffset());

        m_numberOfInFlowChildrenOnFirstLine = -1;

        RenderBlock::startDelayUpdateScrollInfo();

        prepareOrderIteratorAndMargins();

        ChildFrameRects oldChildRects;
        appendChildFrameRects(oldChildRects);

        layoutFlexItems(relayoutChildren);

        RenderBlock::finishDelayUpdateScrollInfo();

        if (logicalHeight() != previousHeight)
            relayoutChildren = true;

        layoutPositionedObjects(relayoutChildren || isRoot());

        computeRegionRangeForBlock(flowThreadContainingBlock());

        repaintChildrenDuringLayoutIfMoved(oldChildRects);
        // FIXME: css3/flexbox/repaint-rtl-column.html seems to repaint more overflow than it needs to.
        computeOverflow(clientLogicalBottomAfterRepositioning());
    }

    updateLayerTransform();

    // Update our scroll information if we're overflow:auto/scroll/hidden now that we know if
    // we overflow or not.
    updateScrollInfoAfterLayout();

    repainter.repaintAfterLayout();

    clearNeedsLayout();
}

void RenderFlexibleBox::appendChildFrameRects(ChildFrameRects& childFrameRects)
{
    for (RenderBox* child = m_orderIterator.first(); child; child = m_orderIterator.next()) {
        if (!child->isOutOfFlowPositioned())
            childFrameRects.append(child->frameRect());
    }
}

void RenderFlexibleBox::repaintChildrenDuringLayoutIfMoved(const ChildFrameRects& oldChildRects)
{
    size_t childIndex = 0;
    for (RenderBox* child = m_orderIterator.first(); child; child = m_orderIterator.next()) {
        if (child->isOutOfFlowPositioned())
            continue;

        // If the child moved, we have to repaint it as well as any floating/positioned
        // descendants. An exception is if we need a layout. In this case, we know we're going to
        // repaint ourselves (and the child) anyway.
        if (!selfNeedsLayout() && child->checkForRepaintDuringLayout())
            child->repaintDuringLayoutIfMoved(oldChildRects[childIndex]);
        ++childIndex;
    }
    ASSERT(childIndex == oldChildRects.size());
}

void RenderFlexibleBox::paintChildren(PaintInfo& paintInfo, const LayoutPoint& paintOffset)
{
    for (RenderBox* child = m_orderIterator.first(); child; child = m_orderIterator.next())
        paintChildAsInlineBlock(child, paintInfo, paintOffset);
}

void RenderFlexibleBox::repositionLogicalHeightDependentFlexItems(Vector<LineContext>& lineContexts)
{
    LayoutUnit crossAxisStartEdge = lineContexts.isEmpty() ? LayoutUnit() : lineContexts[0].crossAxisOffset;
    alignFlexLines(lineContexts);

    // If we have a single line flexbox, the line height is all the available space.
    // For flex-direction: row, this means we need to use the height, so we do this after calling updateLogicalHeight.
    if (!isMultiline() && lineContexts.size() == 1)
        lineContexts[0].crossAxisExtent = crossAxisContentExtent();
    alignChildren(lineContexts);

    if (style()->flexWrap() == FlexWrapReverse)
        flipForWrapReverse(lineContexts, crossAxisStartEdge);

    // direction:rtl + flex-direction:column means the cross-axis direction is flipped.
    flipForRightToLeftColumn();
}

LayoutUnit RenderFlexibleBox::clientLogicalBottomAfterRepositioning()
{
    LayoutUnit maxChildLogicalBottom = 0;
    for (RenderBox* child = firstChildBox(); child; child = child->nextSiblingBox()) {
        if (child->isOutOfFlowPositioned())
            continue;
        LayoutUnit childLogicalBottom = logicalTopForChild(child) + logicalHeightForChild(child) + marginAfterForChild(child);
        maxChildLogicalBottom = std::max(maxChildLogicalBottom, childLogicalBottom);
    }
    return std::max(clientLogicalBottom(), maxChildLogicalBottom + paddingAfter());
}

bool RenderFlexibleBox::hasOrthogonalFlow(RenderBox* child) const
{
    // FIXME: If the child is a flexbox, then we need to check isHorizontalFlow.
    return isHorizontalFlow() != child->isHorizontalWritingMode();
}

bool RenderFlexibleBox::isColumnFlow() const
{
    return style()->isColumnFlexDirection();
}

bool RenderFlexibleBox::isHorizontalFlow() const
{
    if (isHorizontalWritingMode())
        return !isColumnFlow();
    return isColumnFlow();
}

bool RenderFlexibleBox::isLeftToRightFlow() const
{
    if (isColumnFlow())
        return style()->writingMode() == TopToBottomWritingMode || style()->writingMode() == LeftToRightWritingMode;
    return style()->isLeftToRightDirection() ^ (style()->flexDirection() == FlowRowReverse);
}

bool RenderFlexibleBox::isMultiline() const
{
    return style()->flexWrap() != FlexNoWrap;
}

Length RenderFlexibleBox::flexBasisForChild(RenderBox* child) const
{
    Length flexLength = child->style()->flexBasis();
    if (flexLength.isAuto())
        flexLength = isHorizontalFlow() ? child->style()->width() : child->style()->height();
    return flexLength;
}

void RenderFlexibleBox::setCrossAxisExtent(LayoutUnit extent)
{
    if (isHorizontalFlow())
        setHeight(extent);
    else
        setWidth(extent);
}

LayoutUnit RenderFlexibleBox::crossAxisExtentForChild(RenderBox* child) const
{
    return isHorizontalFlow() ? child->height() : child->width();
}

LayoutUnit RenderFlexibleBox::mainAxisExtentForChild(RenderBox* child) const
{
    return isHorizontalFlow() ? child->width() : child->height();
}

LayoutUnit RenderFlexibleBox::crossAxisExtent() const
{
    return isHorizontalFlow() ? height() : width();
}

LayoutUnit RenderFlexibleBox::mainAxisExtent() const
{
    return isHorizontalFlow() ? width() : height();
}

LayoutUnit RenderFlexibleBox::crossAxisContentExtent() const
{
    return isHorizontalFlow() ? contentHeight() : contentWidth();
}

LayoutUnit RenderFlexibleBox::mainAxisContentExtent(LayoutUnit contentLogicalHeight)
{
    if (isColumnFlow()) {
        LogicalExtentComputedValues computedValues;
        LayoutUnit borderPaddingAndScrollbar = borderAndPaddingLogicalHeight() + scrollbarLogicalHeight();
        // FIXME: Remove this std:max once we enable saturated layout arithmetic. It's just here to handle overflow.
        LayoutUnit borderBoxLogicalHeight = std::max(contentLogicalHeight, contentLogicalHeight + borderPaddingAndScrollbar);
        computeLogicalHeight(borderBoxLogicalHeight, logicalTop(), computedValues);
        if (computedValues.m_extent == LayoutUnit::max())
            return computedValues.m_extent;
        return std::max(LayoutUnit(0), computedValues.m_extent - borderPaddingAndScrollbar);
    }
    return contentLogicalWidth();
}

LayoutUnit RenderFlexibleBox::computeMainAxisExtentForChild(RenderBox* child, SizeType sizeType, const Length& size)
{
    // FIXME: This is wrong for orthogonal flows. It should use the flexbox's writing-mode, not the child's in order
    // to figure out the logical height/width.
    if (isColumnFlow()) {
        // We don't have to check for "auto" here - computeContentLogicalHeight will just return -1 for that case anyway.
        if (size.isIntrinsic())
            child->layoutIfNeeded();
        return child->computeContentLogicalHeight(size, child->logicalHeight() - child->borderAndPaddingLogicalHeight());
    }
    return child->computeLogicalWidthUsing(sizeType, size, contentLogicalWidth(), this) - child->borderAndPaddingLogicalWidth();
}

WritingMode RenderFlexibleBox::transformedWritingMode() const
{
    WritingMode mode = style()->writingMode();
    if (!isColumnFlow())
        return mode;

    switch (mode) {
    case TopToBottomWritingMode:
    case BottomToTopWritingMode:
        return style()->isLeftToRightDirection() ? LeftToRightWritingMode : RightToLeftWritingMode;
    case LeftToRightWritingMode:
    case RightToLeftWritingMode:
        return style()->isLeftToRightDirection() ? TopToBottomWritingMode : BottomToTopWritingMode;
    }
    ASSERT_NOT_REACHED();
    return TopToBottomWritingMode;
}

LayoutUnit RenderFlexibleBox::flowAwareBorderStart() const
{
    if (isHorizontalFlow())
        return isLeftToRightFlow() ? borderLeft() : borderRight();
    return isLeftToRightFlow() ? borderTop() : borderBottom();
}

LayoutUnit RenderFlexibleBox::flowAwareBorderEnd() const
{
    if (isHorizontalFlow())
        return isLeftToRightFlow() ? borderRight() : borderLeft();
    return isLeftToRightFlow() ? borderBottom() : borderTop();
}

LayoutUnit RenderFlexibleBox::flowAwareBorderBefore() const
{
    switch (transformedWritingMode()) {
    case TopToBottomWritingMode:
        return borderTop();
    case BottomToTopWritingMode:
        return borderBottom();
    case LeftToRightWritingMode:
        return borderLeft();
    case RightToLeftWritingMode:
        return borderRight();
    }
    ASSERT_NOT_REACHED();
    return borderTop();
}

LayoutUnit RenderFlexibleBox::flowAwareBorderAfter() const
{
    switch (transformedWritingMode()) {
    case TopToBottomWritingMode:
        return borderBottom();
    case BottomToTopWritingMode:
        return borderTop();
    case LeftToRightWritingMode:
        return borderRight();
    case RightToLeftWritingMode:
        return borderLeft();
    }
    ASSERT_NOT_REACHED();
    return borderTop();
}

LayoutUnit RenderFlexibleBox::flowAwarePaddingStart() const
{
    if (isHorizontalFlow())
        return isLeftToRightFlow() ? paddingLeft() : paddingRight();
    return isLeftToRightFlow() ? paddingTop() : paddingBottom();
}

LayoutUnit RenderFlexibleBox::flowAwarePaddingEnd() const
{
    if (isHorizontalFlow())
        return isLeftToRightFlow() ? paddingRight() : paddingLeft();
    return isLeftToRightFlow() ? paddingBottom() : paddingTop();
}

LayoutUnit RenderFlexibleBox::flowAwarePaddingBefore() const
{
    switch (transformedWritingMode()) {
    case TopToBottomWritingMode:
        return paddingTop();
    case BottomToTopWritingMode:
        return paddingBottom();
    case LeftToRightWritingMode:
        return paddingLeft();
    case RightToLeftWritingMode:
        return paddingRight();
    }
    ASSERT_NOT_REACHED();
    return paddingTop();
}

LayoutUnit RenderFlexibleBox::flowAwarePaddingAfter() const
{
    switch (transformedWritingMode()) {
    case TopToBottomWritingMode:
        return paddingBottom();
    case BottomToTopWritingMode:
        return paddingTop();
    case LeftToRightWritingMode:
        return paddingRight();
    case RightToLeftWritingMode:
        return paddingLeft();
    }
    ASSERT_NOT_REACHED();
    return paddingTop();
}

LayoutUnit RenderFlexibleBox::flowAwareMarginStartForChild(RenderBox* child) const
{
    if (isHorizontalFlow())
        return isLeftToRightFlow() ? child->marginLeft() : child->marginRight();
    return isLeftToRightFlow() ? child->marginTop() : child->marginBottom();
}

LayoutUnit RenderFlexibleBox::flowAwareMarginEndForChild(RenderBox* child) const
{
    if (isHorizontalFlow())
        return isLeftToRightFlow() ? child->marginRight() : child->marginLeft();
    return isLeftToRightFlow() ? child->marginBottom() : child->marginTop();
}

LayoutUnit RenderFlexibleBox::flowAwareMarginBeforeForChild(RenderBox* child) const
{
    switch (transformedWritingMode()) {
    case TopToBottomWritingMode:
        return child->marginTop();
    case BottomToTopWritingMode:
        return child->marginBottom();
    case LeftToRightWritingMode:
        return child->marginLeft();
    case RightToLeftWritingMode:
        return child->marginRight();
    }
    ASSERT_NOT_REACHED();
    return marginTop();
}

LayoutUnit RenderFlexibleBox::flowAwareMarginAfterForChild(RenderBox* child) const
{
    switch (transformedWritingMode()) {
    case TopToBottomWritingMode:
        return child->marginBottom();
    case BottomToTopWritingMode:
        return child->marginTop();
    case LeftToRightWritingMode:
        return child->marginRight();
    case RightToLeftWritingMode:
        return child->marginLeft();
    }
    ASSERT_NOT_REACHED();
    return marginBottom();
}

LayoutUnit RenderFlexibleBox::crossAxisMarginExtentForChild(RenderBox* child) const
{
    return isHorizontalFlow() ? child->marginHeight() : child->marginWidth();
}

LayoutUnit RenderFlexibleBox::crossAxisScrollbarExtent() const
{
    return isHorizontalFlow() ? horizontalScrollbarHeight() : verticalScrollbarWidth();
}

LayoutPoint RenderFlexibleBox::flowAwareLocationForChild(RenderBox* child) const
{
    return isHorizontalFlow() ? child->location() : child->location().transposedPoint();
}

void RenderFlexibleBox::setFlowAwareLocationForChild(RenderBox* child, const LayoutPoint& location)
{
    if (isHorizontalFlow())
        child->setLocation(location);
    else
        child->setLocation(location.transposedPoint());
}

LayoutUnit RenderFlexibleBox::mainAxisBorderAndPaddingExtentForChild(RenderBox* child) const
{
    return isHorizontalFlow() ? child->borderAndPaddingWidth() : child->borderAndPaddingHeight();
}

LayoutUnit RenderFlexibleBox::mainAxisScrollbarExtentForChild(RenderBox* child) const
{
    return isHorizontalFlow() ? child->verticalScrollbarWidth() : child->horizontalScrollbarHeight();
}

static inline bool preferredMainAxisExtentDependsOnLayout(const Length& flexBasis, bool hasInfiniteLineLength)
{
    return flexBasis.isAuto() || (flexBasis.isFixed() && !flexBasis.value() && hasInfiniteLineLength);
}

bool RenderFlexibleBox::childPreferredMainAxisContentExtentRequiresLayout(RenderBox* child, bool hasInfiniteLineLength) const
{
    return preferredMainAxisExtentDependsOnLayout(flexBasisForChild(child), hasInfiniteLineLength) && hasOrthogonalFlow(child);
}

LayoutUnit RenderFlexibleBox::preferredMainAxisContentExtentForChild(RenderBox* child, bool hasInfiniteLineLength, bool relayoutChildren)
{
    child->clearOverrideSize();

    Length flexBasis = flexBasisForChild(child);
    if (preferredMainAxisExtentDependsOnLayout(flexBasis, hasInfiniteLineLength)) {
        LayoutUnit mainAxisExtent;
        if (hasOrthogonalFlow(child)) {
            if (child->needsLayout() || relayoutChildren) {
                m_intrinsicSizeAlongMainAxis.remove(child);
                child->forceChildLayout();
                m_intrinsicSizeAlongMainAxis.set(child, child->logicalHeight());
            }
            ASSERT(m_intrinsicSizeAlongMainAxis.contains(child));
            mainAxisExtent = m_intrinsicSizeAlongMainAxis.get(child);
        } else {
            mainAxisExtent = child->maxPreferredLogicalWidth();
        }
        ASSERT(mainAxisExtent - mainAxisBorderAndPaddingExtentForChild(child) >= 0);
        return mainAxisExtent - mainAxisBorderAndPaddingExtentForChild(child);
    }
    return std::max(LayoutUnit(0), computeMainAxisExtentForChild(child, MainOrPreferredSize, flexBasis));
}

void RenderFlexibleBox::layoutFlexItems(bool relayoutChildren)
{
    Vector<LineContext> lineContexts;
    OrderedFlexItemList orderedChildren;
    LayoutUnit sumFlexBaseSize;
    double totalFlexGrow;
    double totalWeightedFlexShrink;
    LayoutUnit sumHypotheticalMainSize;

    Vector<LayoutUnit, 16> childSizes;

    m_orderIterator.first();
    LayoutUnit crossAxisOffset = flowAwareBorderBefore() + flowAwarePaddingBefore();
    bool hasInfiniteLineLength = false;
    while (computeNextFlexLine(orderedChildren, sumFlexBaseSize, totalFlexGrow, totalWeightedFlexShrink, sumHypotheticalMainSize, hasInfiniteLineLength, relayoutChildren)) {
        LayoutUnit containerMainInnerSize = mainAxisContentExtent(sumHypotheticalMainSize);
        LayoutUnit availableFreeSpace = containerMainInnerSize - sumFlexBaseSize;
        FlexSign flexSign = (sumHypotheticalMainSize < containerMainInnerSize) ? PositiveFlexibility : NegativeFlexibility;
        InflexibleFlexItemSize inflexibleItems;
        childSizes.reserveCapacity(orderedChildren.size());
        while (!resolveFlexibleLengths(flexSign, orderedChildren, availableFreeSpace, totalFlexGrow, totalWeightedFlexShrink, inflexibleItems, childSizes, hasInfiniteLineLength)) {
            ASSERT(totalFlexGrow >= 0 && totalWeightedFlexShrink >= 0);
            ASSERT(inflexibleItems.size() > 0);
        }

        layoutAndPlaceChildren(crossAxisOffset, orderedChildren, childSizes, availableFreeSpace, relayoutChildren, lineContexts, hasInfiniteLineLength);
    }
    if (hasLineIfEmpty()) {
        // Even if computeNextFlexLine returns true, the flexbox might not have
        // a line because all our children might be out of flow positioned.
        // Instead of just checking if we have a line, make sure the flexbox
        // has at least a line's worth of height to cover this case.
        LayoutUnit minHeight = borderAndPaddingLogicalHeight()
            + lineHeight(true, isHorizontalWritingMode() ? HorizontalLine : VerticalLine, PositionOfInteriorLineBoxes)
            + scrollbarLogicalHeight();
        if (height() < minHeight)
            setLogicalHeight(minHeight);
    }

    updateLogicalHeight();
    repositionLogicalHeightDependentFlexItems(lineContexts);
}

LayoutUnit RenderFlexibleBox::autoMarginOffsetInMainAxis(const OrderedFlexItemList& children, LayoutUnit& availableFreeSpace)
{
    if (availableFreeSpace <= 0)
        return 0;

    int numberOfAutoMargins = 0;
    bool isHorizontal = isHorizontalFlow();
    for (size_t i = 0; i < children.size(); ++i) {
        RenderBox* child = children[i];
        if (child->isOutOfFlowPositioned())
            continue;
        if (isHorizontal) {
            if (child->style()->marginLeft().isAuto())
                ++numberOfAutoMargins;
            if (child->style()->marginRight().isAuto())
                ++numberOfAutoMargins;
        } else {
            if (child->style()->marginTop().isAuto())
                ++numberOfAutoMargins;
            if (child->style()->marginBottom().isAuto())
                ++numberOfAutoMargins;
        }
    }
    if (!numberOfAutoMargins)
        return 0;

    LayoutUnit sizeOfAutoMargin = availableFreeSpace / numberOfAutoMargins;
    availableFreeSpace = 0;
    return sizeOfAutoMargin;
}

void RenderFlexibleBox::updateAutoMarginsInMainAxis(RenderBox* child, LayoutUnit autoMarginOffset)
{
    ASSERT(autoMarginOffset >= 0);

    if (isHorizontalFlow()) {
        if (child->style()->marginLeft().isAuto())
            child->setMarginLeft(autoMarginOffset);
        if (child->style()->marginRight().isAuto())
            child->setMarginRight(autoMarginOffset);
    } else {
        if (child->style()->marginTop().isAuto())
            child->setMarginTop(autoMarginOffset);
        if (child->style()->marginBottom().isAuto())
            child->setMarginBottom(autoMarginOffset);
    }
}

bool RenderFlexibleBox::hasAutoMarginsInCrossAxis(RenderBox* child) const
{
    if (isHorizontalFlow())
        return child->style()->marginTop().isAuto() || child->style()->marginBottom().isAuto();
    return child->style()->marginLeft().isAuto() || child->style()->marginRight().isAuto();
}

LayoutUnit RenderFlexibleBox::availableAlignmentSpaceForChild(LayoutUnit lineCrossAxisExtent, RenderBox* child)
{
    ASSERT(!child->isOutOfFlowPositioned());
    LayoutUnit childCrossExtent = crossAxisMarginExtentForChild(child) + crossAxisExtentForChild(child);
    return lineCrossAxisExtent - childCrossExtent;
}

bool RenderFlexibleBox::updateAutoMarginsInCrossAxis(RenderBox* child, LayoutUnit availableAlignmentSpace)
{
    ASSERT(!child->isOutOfFlowPositioned());
    ASSERT(availableAlignmentSpace >= 0);

    bool isHorizontal = isHorizontalFlow();
    Length topOrLeft = isHorizontal ? child->style()->marginTop() : child->style()->marginLeft();
    Length bottomOrRight = isHorizontal ? child->style()->marginBottom() : child->style()->marginRight();
    if (topOrLeft.isAuto() && bottomOrRight.isAuto()) {
        adjustAlignmentForChild(child, availableAlignmentSpace / 2);
        if (isHorizontal) {
            child->setMarginTop(availableAlignmentSpace / 2);
            child->setMarginBottom(availableAlignmentSpace / 2);
        } else {
            child->setMarginLeft(availableAlignmentSpace / 2);
            child->setMarginRight(availableAlignmentSpace / 2);
        }
        return true;
    }
    bool shouldAdjustTopOrLeft = true;
    if (isColumnFlow() && !child->style()->isLeftToRightDirection()) {
        // For column flows, only make this adjustment if topOrLeft corresponds to the "before" margin,
        // so that flipForRightToLeftColumn will do the right thing.
        shouldAdjustTopOrLeft = false;
    }
    if (!isColumnFlow() && child->style()->isFlippedBlocksWritingMode()) {
        // If we are a flipped writing mode, we need to adjust the opposite side. This is only needed
        // for row flows because this only affects the block-direction axis.
        shouldAdjustTopOrLeft = false;
    }

    if (topOrLeft.isAuto()) {
        if (shouldAdjustTopOrLeft)
            adjustAlignmentForChild(child, availableAlignmentSpace);

        if (isHorizontal)
            child->setMarginTop(availableAlignmentSpace);
        else
            child->setMarginLeft(availableAlignmentSpace);
        return true;
    }
    if (bottomOrRight.isAuto()) {
        if (!shouldAdjustTopOrLeft)
            adjustAlignmentForChild(child, availableAlignmentSpace);

        if (isHorizontal)
            child->setMarginBottom(availableAlignmentSpace);
        else
            child->setMarginRight(availableAlignmentSpace);
        return true;
    }
    return false;
}

LayoutUnit RenderFlexibleBox::marginBoxAscentForChild(RenderBox* child)
{
    LayoutUnit ascent = child->firstLineBoxBaseline();
    if (ascent == -1)
        ascent = crossAxisExtentForChild(child);
    return ascent + flowAwareMarginBeforeForChild(child);
}

LayoutUnit RenderFlexibleBox::computeChildMarginValue(Length margin)
{
    // When resolving the margins, we use the content size for resolving percent and calc (for percents in calc expressions) margins.
    // Fortunately, percent margins are always computed with respect to the block's width, even for margin-top and margin-bottom.
    LayoutUnit availableSize = contentLogicalWidth();
    return minimumValueForLength(margin, availableSize);
}

void RenderFlexibleBox::prepareOrderIteratorAndMargins()
{
    OrderIteratorPopulator populator(m_orderIterator);

    for (RenderBox* child = firstChildBox(); child; child = child->nextSiblingBox()) {
        populator.collectChild(child);

        if (child->isOutOfFlowPositioned())
            continue;

        // Before running the flex algorithm, 'auto' has a margin of 0.
        // Also, if we're not auto sizing, we don't do a layout that computes the start/end margins.
        if (isHorizontalFlow()) {
            child->setMarginLeft(computeChildMarginValue(child->style()->marginLeft()));
            child->setMarginRight(computeChildMarginValue(child->style()->marginRight()));
        } else {
            child->setMarginTop(computeChildMarginValue(child->style()->marginTop()));
            child->setMarginBottom(computeChildMarginValue(child->style()->marginBottom()));
        }
    }
}

LayoutUnit RenderFlexibleBox::adjustChildSizeForMinAndMax(RenderBox* child, LayoutUnit childSize)
{
    Length max = isHorizontalFlow() ? child->style()->maxWidth() : child->style()->maxHeight();
    if (max.isSpecifiedOrIntrinsic()) {
        LayoutUnit maxExtent = computeMainAxisExtentForChild(child, MaxSize, max);
        if (maxExtent != -1 && childSize > maxExtent)
            childSize = maxExtent;
    }

    Length min = isHorizontalFlow() ? child->style()->minWidth() : child->style()->minHeight();
    LayoutUnit minExtent = 0;
    if (min.isSpecifiedOrIntrinsic())
        minExtent = computeMainAxisExtentForChild(child, MinSize, min);
    return std::max(childSize, minExtent);
}

bool RenderFlexibleBox::computeNextFlexLine(OrderedFlexItemList& orderedChildren, LayoutUnit& sumFlexBaseSize, double& totalFlexGrow, double& totalWeightedFlexShrink, LayoutUnit& sumHypotheticalMainSize, bool& hasInfiniteLineLength, bool relayoutChildren)
{
    orderedChildren.clear();
    sumFlexBaseSize = 0;
    totalFlexGrow = totalWeightedFlexShrink = 0;
    sumHypotheticalMainSize = 0;

    if (!m_orderIterator.currentChild())
        return false;

    LayoutUnit lineBreakLength = mainAxisContentExtent(LayoutUnit::max());
    hasInfiniteLineLength = lineBreakLength == LayoutUnit::max();

    bool lineHasInFlowItem = false;

    for (RenderBox* child = m_orderIterator.currentChild(); child; child = m_orderIterator.next()) {
        if (child->isOutOfFlowPositioned()) {
            orderedChildren.append(child);
            continue;
        }

        LayoutUnit childMainAxisExtent = preferredMainAxisContentExtentForChild(child, hasInfiniteLineLength, relayoutChildren);
        LayoutUnit childMainAxisMarginBorderPadding = mainAxisBorderAndPaddingExtentForChild(child)
            + (isHorizontalFlow() ? child->marginWidth() : child->marginHeight());
        LayoutUnit childFlexBaseSize = childMainAxisExtent + childMainAxisMarginBorderPadding;

        LayoutUnit childMinMaxAppliedMainAxisExtent = adjustChildSizeForMinAndMax(child, childMainAxisExtent);
        LayoutUnit childHypotheticalMainSize = childMinMaxAppliedMainAxisExtent + childMainAxisMarginBorderPadding;

        if (isMultiline() && sumHypotheticalMainSize + childHypotheticalMainSize > lineBreakLength && lineHasInFlowItem)
            break;
        orderedChildren.append(child);
        lineHasInFlowItem  = true;
        sumFlexBaseSize += childFlexBaseSize;
        totalFlexGrow += child->style()->flexGrow();
        totalWeightedFlexShrink += child->style()->flexShrink() * childMainAxisExtent;
        sumHypotheticalMainSize += childHypotheticalMainSize;
    }
    return true;
}

void RenderFlexibleBox::freezeViolations(const Vector<Violation>& violations, LayoutUnit& availableFreeSpace, double& totalFlexGrow, double& totalWeightedFlexShrink, InflexibleFlexItemSize& inflexibleItems, bool hasInfiniteLineLength)
{
    for (size_t i = 0; i < violations.size(); ++i) {
        RenderBox* child = violations[i].child;
        LayoutUnit childSize = violations[i].childSize;
        LayoutUnit preferredChildSize = preferredMainAxisContentExtentForChild(child, hasInfiniteLineLength);
        availableFreeSpace -= childSize - preferredChildSize;
        totalFlexGrow -= child->style()->flexGrow();
        totalWeightedFlexShrink -= child->style()->flexShrink() * preferredChildSize;
        inflexibleItems.set(child, childSize);
    }
}

// Returns true if we successfully ran the algorithm and sized the flex items.
bool RenderFlexibleBox::resolveFlexibleLengths(FlexSign flexSign, const OrderedFlexItemList& children, LayoutUnit& availableFreeSpace, double& totalFlexGrow, double& totalWeightedFlexShrink, InflexibleFlexItemSize& inflexibleItems, Vector<LayoutUnit, 16>& childSizes, bool hasInfiniteLineLength)
{
    childSizes.resize(0);
    LayoutUnit totalViolation = 0;
    LayoutUnit usedFreeSpace = 0;
    Vector<Violation> minViolations;
    Vector<Violation> maxViolations;
    for (size_t i = 0; i < children.size(); ++i) {
        RenderBox* child = children[i];
        if (child->isOutOfFlowPositioned()) {
            childSizes.append(0);
            continue;
        }

        if (inflexibleItems.contains(child))
            childSizes.append(inflexibleItems.get(child));
        else {
            LayoutUnit preferredChildSize = preferredMainAxisContentExtentForChild(child, hasInfiniteLineLength);
            LayoutUnit childSize = preferredChildSize;
            double extraSpace = 0;
            if (availableFreeSpace > 0 && totalFlexGrow > 0 && flexSign == PositiveFlexibility && std::isfinite(totalFlexGrow))
                extraSpace = availableFreeSpace * child->style()->flexGrow() / totalFlexGrow;
            else if (availableFreeSpace < 0 && totalWeightedFlexShrink > 0 && flexSign == NegativeFlexibility && std::isfinite(totalWeightedFlexShrink))
                extraSpace = availableFreeSpace * child->style()->flexShrink() * preferredChildSize / totalWeightedFlexShrink;
            if (std::isfinite(extraSpace))
                childSize += LayoutUnit::fromFloatRound(extraSpace);

            LayoutUnit adjustedChildSize = adjustChildSizeForMinAndMax(child, childSize);
            childSizes.append(adjustedChildSize);
            usedFreeSpace += adjustedChildSize - preferredChildSize;

            LayoutUnit violation = adjustedChildSize - childSize;
            if (violation > 0)
                minViolations.append(Violation(child, adjustedChildSize));
            else if (violation < 0)
                maxViolations.append(Violation(child, adjustedChildSize));
            totalViolation += violation;
        }
    }

    if (totalViolation)
        freezeViolations(totalViolation < 0 ? maxViolations : minViolations, availableFreeSpace, totalFlexGrow, totalWeightedFlexShrink, inflexibleItems, hasInfiniteLineLength);
    else
        availableFreeSpace -= usedFreeSpace;

    return !totalViolation;
}

static LayoutUnit initialJustifyContentOffset(LayoutUnit availableFreeSpace, EJustifyContent justifyContent, unsigned numberOfChildren)
{
    if (justifyContent == JustifyFlexEnd)
        return availableFreeSpace;
    if (justifyContent == JustifyCenter)
        return availableFreeSpace / 2;
    if (justifyContent == JustifySpaceAround) {
        if (availableFreeSpace > 0 && numberOfChildren)
            return availableFreeSpace / (2 * numberOfChildren);
        else
            return availableFreeSpace / 2;
    }
    return 0;
}

static LayoutUnit justifyContentSpaceBetweenChildren(LayoutUnit availableFreeSpace, EJustifyContent justifyContent, unsigned numberOfChildren)
{
    if (availableFreeSpace > 0 && numberOfChildren > 1) {
        if (justifyContent == JustifySpaceBetween)
            return availableFreeSpace / (numberOfChildren - 1);
        if (justifyContent == JustifySpaceAround)
            return availableFreeSpace / numberOfChildren;
    }
    return 0;
}

void RenderFlexibleBox::setLogicalOverrideSize(RenderBox* child, LayoutUnit childPreferredSize)
{
    if (hasOrthogonalFlow(child))
        child->setOverrideLogicalContentHeight(childPreferredSize - child->borderAndPaddingLogicalHeight());
    else
        child->setOverrideLogicalContentWidth(childPreferredSize - child->borderAndPaddingLogicalWidth());
}

void RenderFlexibleBox::prepareChildForPositionedLayout(RenderBox* child, LayoutUnit mainAxisOffset, LayoutUnit crossAxisOffset, PositionedLayoutMode layoutMode)
{
    ASSERT(child->isOutOfFlowPositioned());
    child->containingBlock()->insertPositionedObject(child);
    RenderLayer* childLayer = child->layer();
    LayoutUnit inlinePosition = isColumnFlow() ? crossAxisOffset : mainAxisOffset;
    if (layoutMode == FlipForRowReverse && style()->flexDirection() == FlowRowReverse)
        inlinePosition = mainAxisExtent() - mainAxisOffset;
    childLayer->setStaticInlinePosition(inlinePosition);

    LayoutUnit staticBlockPosition = isColumnFlow() ? mainAxisOffset : crossAxisOffset;
    if (childLayer->staticBlockPosition() != staticBlockPosition) {
        childLayer->setStaticBlockPosition(staticBlockPosition);
        if (child->style()->hasStaticBlockPosition(style()->isHorizontalWritingMode()))
            child->setChildNeedsLayout(MarkOnlyThis);
    }
}

ItemPosition RenderFlexibleBox::alignmentForChild(RenderBox* child) const
{
    ItemPosition align = resolveAlignment(style(), child->style());

    if (align == ItemPositionBaseline && hasOrthogonalFlow(child))
        align = ItemPositionFlexStart;

    if (style()->flexWrap() == FlexWrapReverse) {
        if (align == ItemPositionFlexStart)
            align = ItemPositionFlexEnd;
        else if (align == ItemPositionFlexEnd)
            align = ItemPositionFlexStart;
    }

    return align;
}

size_t RenderFlexibleBox::numberOfInFlowPositionedChildren(const OrderedFlexItemList& children) const
{
    size_t count = 0;
    for (size_t i = 0; i < children.size(); ++i) {
        RenderBox* child = children[i];
        if (!child->isOutOfFlowPositioned())
            ++count;
    }
    return count;
}

void RenderFlexibleBox::resetAutoMarginsAndLogicalTopInCrossAxis(RenderBox* child)
{
    if (hasAutoMarginsInCrossAxis(child)) {
        child->updateLogicalHeight();
        if (isHorizontalFlow()) {
            if (child->style()->marginTop().isAuto())
                child->setMarginTop(0);
            if (child->style()->marginBottom().isAuto())
                child->setMarginBottom(0);
        } else {
            if (child->style()->marginLeft().isAuto())
                child->setMarginLeft(0);
            if (child->style()->marginRight().isAuto())
                child->setMarginRight(0);
        }
    }
}

void RenderFlexibleBox::layoutAndPlaceChildren(LayoutUnit& crossAxisOffset, const OrderedFlexItemList& children, const Vector<LayoutUnit, 16>& childSizes, LayoutUnit availableFreeSpace, bool relayoutChildren, Vector<LineContext>& lineContexts, bool hasInfiniteLineLength)
{
    ASSERT(childSizes.size() == children.size());

    size_t numberOfChildrenForJustifyContent = numberOfInFlowPositionedChildren(children);
    LayoutUnit autoMarginOffset = autoMarginOffsetInMainAxis(children, availableFreeSpace);
    LayoutUnit mainAxisOffset = flowAwareBorderStart() + flowAwarePaddingStart();
    mainAxisOffset += initialJustifyContentOffset(availableFreeSpace, style()->justifyContent(), numberOfChildrenForJustifyContent);
    if (style()->flexDirection() == FlowRowReverse)
        mainAxisOffset += isHorizontalFlow() ? verticalScrollbarWidth() : horizontalScrollbarHeight();

    LayoutUnit totalMainExtent = mainAxisExtent();
    LayoutUnit maxAscent = 0, maxDescent = 0; // Used when align-items: baseline.
    LayoutUnit maxChildCrossAxisExtent = 0;
    size_t seenInFlowPositionedChildren = 0;
    bool shouldFlipMainAxis = !isColumnFlow() && !isLeftToRightFlow();
    for (size_t i = 0; i < children.size(); ++i) {
        RenderBox* child = children[i];
        LayoutRectRecorder recorder(*child);

        if (child->isOutOfFlowPositioned()) {
            prepareChildForPositionedLayout(child, mainAxisOffset, crossAxisOffset, FlipForRowReverse);
            continue;
        }

        LayoutUnit childPreferredSize = childSizes[i] + mainAxisBorderAndPaddingExtentForChild(child);
        setLogicalOverrideSize(child, childPreferredSize);
        if (childPreferredSize != mainAxisExtentForChild(child)) {
            child->setChildNeedsLayout(MarkOnlyThis);
        } else {
            // To avoid double applying margin changes in updateAutoMarginsInCrossAxis, we reset the margins here.
            resetAutoMarginsAndLogicalTopInCrossAxis(child);
        }
        // We may have already forced relayout for orthogonal flowing children in preferredMainAxisContentExtentForChild.
        bool forceChildRelayout = relayoutChildren && !childPreferredMainAxisContentExtentRequiresLayout(child, hasInfiniteLineLength);
        updateBlockChildDirtyBitsBeforeLayout(forceChildRelayout, child);
        child->layoutIfNeeded();

        updateAutoMarginsInMainAxis(child, autoMarginOffset);

        LayoutUnit childCrossAxisMarginBoxExtent;
        if (alignmentForChild(child) == ItemPositionBaseline && !hasAutoMarginsInCrossAxis(child)) {
            LayoutUnit ascent = marginBoxAscentForChild(child);
            LayoutUnit descent = (crossAxisMarginExtentForChild(child) + crossAxisExtentForChild(child)) - ascent;

            maxAscent = std::max(maxAscent, ascent);
            maxDescent = std::max(maxDescent, descent);

            childCrossAxisMarginBoxExtent = maxAscent + maxDescent;
        } else
            childCrossAxisMarginBoxExtent = crossAxisExtentForChild(child) + crossAxisMarginExtentForChild(child);
        if (!isColumnFlow())
            setLogicalHeight(std::max(logicalHeight(), crossAxisOffset + flowAwareBorderAfter() + flowAwarePaddingAfter() + childCrossAxisMarginBoxExtent + crossAxisScrollbarExtent()));
        maxChildCrossAxisExtent = std::max(maxChildCrossAxisExtent, childCrossAxisMarginBoxExtent);

        mainAxisOffset += flowAwareMarginStartForChild(child);

        LayoutUnit childMainExtent = mainAxisExtentForChild(child);
        // In an RTL column situation, this will apply the margin-right/margin-end on the left.
        // This will be fixed later in flipForRightToLeftColumn.
        LayoutPoint childLocation(shouldFlipMainAxis ? totalMainExtent - mainAxisOffset - childMainExtent : mainAxisOffset,
            crossAxisOffset + flowAwareMarginBeforeForChild(child));

        // FIXME: Supporting layout deltas.
        setFlowAwareLocationForChild(child, childLocation);
        mainAxisOffset += childMainExtent + flowAwareMarginEndForChild(child);

        ++seenInFlowPositionedChildren;
        if (seenInFlowPositionedChildren < numberOfChildrenForJustifyContent)
            mainAxisOffset += justifyContentSpaceBetweenChildren(availableFreeSpace, style()->justifyContent(), numberOfChildrenForJustifyContent);
    }

    if (isColumnFlow())
        setLogicalHeight(mainAxisOffset + flowAwareBorderEnd() + flowAwarePaddingEnd() + scrollbarLogicalHeight());

    if (style()->flexDirection() == FlowColumnReverse) {
        // We have to do an extra pass for column-reverse to reposition the flex items since the start depends
        // on the height of the flexbox, which we only know after we've positioned all the flex items.
        updateLogicalHeight();
        layoutColumnReverse(children, crossAxisOffset, availableFreeSpace);
    }

    if (m_numberOfInFlowChildrenOnFirstLine == -1)
        m_numberOfInFlowChildrenOnFirstLine = seenInFlowPositionedChildren;
    lineContexts.append(LineContext(crossAxisOffset, maxChildCrossAxisExtent, children.size(), maxAscent));
    crossAxisOffset += maxChildCrossAxisExtent;
}

void RenderFlexibleBox::layoutColumnReverse(const OrderedFlexItemList& children, LayoutUnit crossAxisOffset, LayoutUnit availableFreeSpace)
{
    // This is similar to the logic in layoutAndPlaceChildren, except we place the children
    // starting from the end of the flexbox. We also don't need to layout anything since we're
    // just moving the children to a new position.
    size_t numberOfChildrenForJustifyContent = numberOfInFlowPositionedChildren(children);
    LayoutUnit mainAxisOffset = logicalHeight() - flowAwareBorderEnd() - flowAwarePaddingEnd();
    mainAxisOffset -= initialJustifyContentOffset(availableFreeSpace, style()->justifyContent(), numberOfChildrenForJustifyContent);
    mainAxisOffset -= isHorizontalFlow() ? verticalScrollbarWidth() : horizontalScrollbarHeight();

    size_t seenInFlowPositionedChildren = 0;
    for (size_t i = 0; i < children.size(); ++i) {
        RenderBox* child = children[i];
        LayoutRectRecorder recorder(*child);

        if (child->isOutOfFlowPositioned()) {
            child->layer()->setStaticBlockPosition(mainAxisOffset);
            continue;
        }
        mainAxisOffset -= mainAxisExtentForChild(child) + flowAwareMarginEndForChild(child);

        setFlowAwareLocationForChild(child, LayoutPoint(mainAxisOffset, crossAxisOffset + flowAwareMarginBeforeForChild(child)));

        mainAxisOffset -= flowAwareMarginStartForChild(child);

        ++seenInFlowPositionedChildren;
        if (seenInFlowPositionedChildren < numberOfChildrenForJustifyContent)
            mainAxisOffset -= justifyContentSpaceBetweenChildren(availableFreeSpace, style()->justifyContent(), numberOfChildrenForJustifyContent);
    }
}

static LayoutUnit initialAlignContentOffset(LayoutUnit availableFreeSpace, EAlignContent alignContent, unsigned numberOfLines)
{
    if (alignContent == AlignContentFlexEnd)
        return availableFreeSpace;
    if (alignContent == AlignContentCenter)
        return availableFreeSpace / 2;
    if (alignContent == AlignContentSpaceAround) {
        if (availableFreeSpace > 0 && numberOfLines)
            return availableFreeSpace / (2 * numberOfLines);
        if (availableFreeSpace < 0)
            return availableFreeSpace / 2;
    }
    return 0;
}

static LayoutUnit alignContentSpaceBetweenChildren(LayoutUnit availableFreeSpace, EAlignContent alignContent, unsigned numberOfLines)
{
    if (availableFreeSpace > 0 && numberOfLines > 1) {
        if (alignContent == AlignContentSpaceBetween)
            return availableFreeSpace / (numberOfLines - 1);
        if (alignContent == AlignContentSpaceAround || alignContent == AlignContentStretch)
            return availableFreeSpace / numberOfLines;
    }
    return 0;
}

void RenderFlexibleBox::alignFlexLines(Vector<LineContext>& lineContexts)
{
    if (!isMultiline() || style()->alignContent() == AlignContentFlexStart)
        return;

    LayoutUnit availableCrossAxisSpace = crossAxisContentExtent();
    for (size_t i = 0; i < lineContexts.size(); ++i)
        availableCrossAxisSpace -= lineContexts[i].crossAxisExtent;

    RenderBox* child = m_orderIterator.first();
    LayoutUnit lineOffset = initialAlignContentOffset(availableCrossAxisSpace, style()->alignContent(), lineContexts.size());
    for (unsigned lineNumber = 0; lineNumber < lineContexts.size(); ++lineNumber) {
        lineContexts[lineNumber].crossAxisOffset += lineOffset;
        for (size_t childNumber = 0; childNumber < lineContexts[lineNumber].numberOfChildren; ++childNumber, child = m_orderIterator.next())
            adjustAlignmentForChild(child, lineOffset);

        if (style()->alignContent() == AlignContentStretch && availableCrossAxisSpace > 0)
            lineContexts[lineNumber].crossAxisExtent += availableCrossAxisSpace / static_cast<unsigned>(lineContexts.size());

        lineOffset += alignContentSpaceBetweenChildren(availableCrossAxisSpace, style()->alignContent(), lineContexts.size());
    }
}

void RenderFlexibleBox::adjustAlignmentForChild(RenderBox* child, LayoutUnit delta)
{
    if (child->isOutOfFlowPositioned()) {
        LayoutUnit staticInlinePosition = child->layer()->staticInlinePosition();
        LayoutUnit staticBlockPosition = child->layer()->staticBlockPosition();
        LayoutUnit mainAxis = isColumnFlow() ? staticBlockPosition : staticInlinePosition;
        LayoutUnit crossAxis = isColumnFlow() ? staticInlinePosition : staticBlockPosition;
        crossAxis += delta;
        prepareChildForPositionedLayout(child, mainAxis, crossAxis, NoFlipForRowReverse);
        return;
    }

    setFlowAwareLocationForChild(child, flowAwareLocationForChild(child) + LayoutSize(0, delta));
}

void RenderFlexibleBox::alignChildren(const Vector<LineContext>& lineContexts)
{
    // Keep track of the space between the baseline edge and the after edge of the box for each line.
    Vector<LayoutUnit> minMarginAfterBaselines;

    RenderBox* child = m_orderIterator.first();
    for (size_t lineNumber = 0; lineNumber < lineContexts.size(); ++lineNumber) {
        LayoutUnit minMarginAfterBaseline = LayoutUnit::max();
        LayoutUnit lineCrossAxisExtent = lineContexts[lineNumber].crossAxisExtent;
        LayoutUnit maxAscent = lineContexts[lineNumber].maxAscent;

        for (size_t childNumber = 0; childNumber < lineContexts[lineNumber].numberOfChildren; ++childNumber, child = m_orderIterator.next()) {
            ASSERT(child);
            if (child->isOutOfFlowPositioned()) {
                if (style()->flexWrap() == FlexWrapReverse)
                    adjustAlignmentForChild(child, lineCrossAxisExtent);
                continue;
            }

            if (updateAutoMarginsInCrossAxis(child, std::max(LayoutUnit(0), availableAlignmentSpaceForChild(lineCrossAxisExtent, child))))
                continue;

            switch (alignmentForChild(child)) {
            case ItemPositionAuto:
                ASSERT_NOT_REACHED();
                break;
            case ItemPositionStretch: {
                applyStretchAlignmentToChild(child, lineCrossAxisExtent);
                // Since wrap-reverse flips cross start and cross end, strech children should be aligned with the cross end.
                if (style()->flexWrap() == FlexWrapReverse)
                    adjustAlignmentForChild(child, availableAlignmentSpaceForChild(lineCrossAxisExtent, child));
                break;
            }
            case ItemPositionFlexStart:
                break;
            case ItemPositionFlexEnd:
                adjustAlignmentForChild(child, availableAlignmentSpaceForChild(lineCrossAxisExtent, child));
                break;
            case ItemPositionCenter:
                adjustAlignmentForChild(child, availableAlignmentSpaceForChild(lineCrossAxisExtent, child) / 2);
                break;
            case ItemPositionBaseline: {
                // FIXME: If we get here in columns, we want the use the descent, except we currently can't get the ascent/descent of orthogonal children.
                // https://bugs.webkit.org/show_bug.cgi?id=98076
                LayoutUnit ascent = marginBoxAscentForChild(child);
                LayoutUnit startOffset = maxAscent - ascent;
                adjustAlignmentForChild(child, startOffset);

                if (style()->flexWrap() == FlexWrapReverse)
                    minMarginAfterBaseline = std::min(minMarginAfterBaseline, availableAlignmentSpaceForChild(lineCrossAxisExtent, child) - startOffset);
                break;
            }
            case ItemPositionSelfStart:
            case ItemPositionSelfEnd:
            case ItemPositionStart:
            case ItemPositionEnd:
            case ItemPositionLeft:
            case ItemPositionRight:
                // FIXME: File a bug about implementing that. The extended grammar
                // is not enabled by default so we shouldn't hit this codepath.
                ASSERT_NOT_REACHED();
                break;
            }
        }
        minMarginAfterBaselines.append(minMarginAfterBaseline);
    }

    if (style()->flexWrap() != FlexWrapReverse)
        return;

    // wrap-reverse flips the cross axis start and end. For baseline alignment, this means we
    // need to align the after edge of baseline elements with the after edge of the flex line.
    child = m_orderIterator.first();
    for (size_t lineNumber = 0; lineNumber < lineContexts.size(); ++lineNumber) {
        LayoutUnit minMarginAfterBaseline = minMarginAfterBaselines[lineNumber];
        for (size_t childNumber = 0; childNumber < lineContexts[lineNumber].numberOfChildren; ++childNumber, child = m_orderIterator.next()) {
            ASSERT(child);
            if (alignmentForChild(child) == ItemPositionBaseline && !hasAutoMarginsInCrossAxis(child) && minMarginAfterBaseline)
                adjustAlignmentForChild(child, minMarginAfterBaseline);
        }
    }
}

void RenderFlexibleBox::applyStretchAlignmentToChild(RenderBox* child, LayoutUnit lineCrossAxisExtent)
{
    if (!isColumnFlow() && child->style()->logicalHeight().isAuto()) {
        // FIXME: If the child has orthogonal flow, then it already has an override height set, so use it.
        if (!hasOrthogonalFlow(child)) {
            LayoutUnit stretchedLogicalHeight = child->logicalHeight() + availableAlignmentSpaceForChild(lineCrossAxisExtent, child);
            ASSERT(!child->needsLayout());
            LayoutUnit desiredLogicalHeight = child->constrainLogicalHeightByMinMax(stretchedLogicalHeight, child->logicalHeight() - child->borderAndPaddingLogicalHeight());

            // FIXME: Can avoid laying out here in some cases. See https://webkit.org/b/87905.
            if (desiredLogicalHeight != child->logicalHeight()) {
                child->setOverrideLogicalContentHeight(desiredLogicalHeight - child->borderAndPaddingLogicalHeight());
                child->setLogicalHeight(0);
                child->forceChildLayout();
            }
        }
    } else if (isColumnFlow() && child->style()->logicalWidth().isAuto()) {
        // FIXME: If the child doesn't have orthogonal flow, then it already has an override width set, so use it.
        if (hasOrthogonalFlow(child)) {
            LayoutUnit childWidth = std::max<LayoutUnit>(0, lineCrossAxisExtent - crossAxisMarginExtentForChild(child));
            childWidth = child->constrainLogicalWidthByMinMax(childWidth, childWidth, this);

            if (childWidth != child->logicalWidth()) {
                child->setOverrideLogicalContentWidth(childWidth - child->borderAndPaddingLogicalWidth());
                child->forceChildLayout();
            }
        }
    }
}

void RenderFlexibleBox::flipForRightToLeftColumn()
{
    if (style()->isLeftToRightDirection() || !isColumnFlow())
        return;

    LayoutUnit crossExtent = crossAxisExtent();
    for (RenderBox* child = m_orderIterator.first(); child; child = m_orderIterator.next()) {
        if (child->isOutOfFlowPositioned())
            continue;
        LayoutPoint location = flowAwareLocationForChild(child);
        // For vertical flows, setFlowAwareLocationForChild will transpose x and y,
        // so using the y axis for a column cross axis extent is correct.
        location.setY(crossExtent - crossAxisExtentForChild(child) - location.y());
        setFlowAwareLocationForChild(child, location);
    }
}

void RenderFlexibleBox::flipForWrapReverse(const Vector<LineContext>& lineContexts, LayoutUnit crossAxisStartEdge)
{
    LayoutUnit contentExtent = crossAxisContentExtent();
    RenderBox* child = m_orderIterator.first();
    for (size_t lineNumber = 0; lineNumber < lineContexts.size(); ++lineNumber) {
        for (size_t childNumber = 0; childNumber < lineContexts[lineNumber].numberOfChildren; ++childNumber, child = m_orderIterator.next()) {
            ASSERT(child);
            LayoutUnit lineCrossAxisExtent = lineContexts[lineNumber].crossAxisExtent;
            LayoutUnit originalOffset = lineContexts[lineNumber].crossAxisOffset - crossAxisStartEdge;
            LayoutUnit newOffset = contentExtent - originalOffset - lineCrossAxisExtent;
            adjustAlignmentForChild(child, newOffset - originalOffset);
        }
    }
}

}
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root/Source/core/rendering/RenderFlexibleBox.cpp

DEFINITIONS
